1. Field of the Invention
This invention relates to lubricants for synthetic fibers such as mono- and multi-filament polyester, nylon, polyolefin, poly(benzimidazole), carbon and glass yarn and particularly lubricants having improved resistance to oxidation at elevated temperatures over 200.degree. C. and characterized by decreased viscosity.
2. Description of the Prior Art
The conversion of nylon, polyester, polyolefin, poly(benzimidazole), carbon or glass fibers into useful yarn for textile manufacture requires the use of a lubricant formulation called the "fiber finish" or "spin finish." The spin finish must control the yarn-to-metal friction to protect the newly spun fiber from fusion or breaks and, in the case of texturing, to insure that proper twist is transferred to the yarn. Synthetic fibers must be drawn and textured or bulked to yield optimum physical properties of strength, increased covering, pleasing hand, and greater warmth. During both texturing and bulking, the yarn is exposed to high temperatures. The demand for faster throughput is now requiring temperatures that approach 220.degree. C. or higher thus placing increased stress on the finish to protect the fiber. In the past, high viscosity products have been employed as spin finish components for high-speed texturing of polyester or nylon. However, in recent years, demand for the high viscosity products has slackened, and the fiber and yarn manufacturers are searching for low viscosity, high thermal stablity fiber finishes.
It is known to use polyoxyalkylene compounds such as block and heteric polymers of ethylene oxide and propylene oxide as spin finishes for the production of synthetic yarns. Heteric and block polyoxyalkylene compounds particularly from ethylene oxide and propylene oxide derived by polymerization with initiators such as bisphenol A and tetrahydrofuran are known as spin finishes for the production of synthetic yarns. However, such products generally are not characterized by both low viscosity and high thermal stability.
U.S. Pat. No. 4,094,797 discloses oxidation stable heteric or block copolymer polyoxyalkylene compositions suitable for the treatment of thermoplastic fibers, particularly polyester and nylon fibers, prior to the processing of such fibers. The polyoxyalkylene compounds are derived from lower alkylene oxides and can be initiated with a difunctional aromatic compound containing reactive hydrogens such as dihydroxyphenol and are capped on at least one end of the chain with an .alpha.-olefin epoxide or mixtures thereof. U.S. Pat. No. 4,134,841 discloses a fiber lubricant composition of enhanced heat stability which comprises a non-hindered polyphenol stabilizer and a polyether lubricant.